This specification relates to stream processing.
Stream processing refers to systems and techniques for continually processing unbounded sequences of data objects, e.g., events, in real time, i.e., a sequence that is not limited to a predetermined number of data objects or rate of arrival of data objects; such a sequence is referred to as a stream. For example, a stream of objects may represent page requests received by a web site, telemetry events from sensors, or microblog messages posted by users. Stream processing systems can perform a variety of tasks, including providing immediate search results as data objects are found and continually processing new data objects as they are received.